1. Field
The disclosed embodiments relate to a process and a device for regulating the luminous intensity of indicator lights of a piece of monitoring and control equipment of a plane when this equipment has displays and indicator lights whose luminous emission sources can be of several types and/or whose luminous intensities must vary in different ways in order to make them easily readable.
2. Brief Description of Related Developments
Monitoring and control equipment in cockpits of airplanes include various control means, generally grouped by functional category, such as switches, push-buttons or selectors often combined with legends, to indicate the function of these different controls and display means, such as digital or alphanumeric value displays and indicator lights. For purposes of assuring that the legends, displays and indicator lights can be easily read under variable lighting conditions linked to the cockpit environment, monitoring and control equipment generally have illumination means, most often consisting of light sources internal to the monitoring and control equipment, to render readable the data displayed on the visible face of this equipment, in particular when the ambient luminosity is low and no longer sufficient to assure correct readability. Indicator lights or displays are considered well readable if, on the one hand, the flight crew can read them comfortably and, on the other hand, the data that said indicator lights or displays present is clear and unambiguous.
Since external lighting conditions vary in significant proportions, for example, between high daytime luminosity, in full sun or under clouds, and the dark of night when the cockpit is poorly lit or unlit, the illumination means for the monitoring and control equipment most often have means for regulating the luminous intensity of legends and displays of this said monitoring and control equipment.
In modern airplanes, these illumination means can use light sources of different types. These light sources are most often of the incandescent or electroluminescent type, in particular, by means of so-called LED diodes. They are used, in particular, to illuminate legends engraved on plates placed on the visible face of the monitoring and control equipment, for lighting numerical or alphanumeric read-outs such as those of liquid crystal displays, [and] for illuminating the legends of luminous push-buttons.
Luminous push-buttons are often pulse controls that generally have a legend over part of their visible surface, for example the lower half, to indicate the function of the push-button.
The other part of the visible surface of the push-buttons generally incorporates a luminous indicator whose lighting device can be integrated inside the luminous push-button. These indicator lights light up to inform the pilot of the status of the function controlled by the corresponding push-button. For example, in such control equipment that permits activating automatic airplane pilots, a push-button used to engage an automatic pilot is lit up when a pilot presses the push-button and the corresponding automatic pilot is engaged. This luminous push-button will turn off if the corresponding automatic pilot is disconnected, whether it is disconnected by a pilot or by any automatic means whatever, so that pilots have information feedback on the status of the function in question directly at the level of the control itself, comprised of the push-button. The lighting and luminous intensity of the luminous push-button legend are independent of the on or off state of the push-button indicator light.
Other indicator lights can be used on the equipment. For example, in order to inform the pilot of the status of certain parameter selections, for example, speed for the needs of the automatic handle of the engine thrust regulator, the indicator light associated with the speed selector will be in a state of illumination when the parameter is active and will be turned off when it is not.
Indicator lights associated with luminous push-buttons or with selectors are often green in color when they are illuminated. This color is frequently used in a conventional manner to indicate normal system functioning.
Due to the diversity of these light-emitting elements and the variety of their light sources, it is difficult to satisfactorily regulate the lighting of all the legends, displays, and indicator lights of a piece of monitoring and control equipment by means of a single regulation control. The majority of current planes have two or more independent controls that permit pilots to adjust the luminous intensity of the different light sources on said monitoring and control equipment in an independent manner, as a function of readability constraints.
Since readability constraints are different for legends and for indicator lights, and in practice these constraints are greater for legends, certain airplanes have a continuous control for regulating the lighting of legends on plates and displays and another two-position control to select between two predetermined values of luminous intensity for luminous push-button and selector indicator lights. For this other control, a first position called “day” corresponds to a high luminosity of the indicator lights of luminous push-buttons and selectors so they can be read under conditions of high ambient luminosity, and a second position called “night” or “DIM” corresponds to a reduced luminosity of these indicator lights for conditions of reduced ambient luminosity.
Nevertheless, for this second “night” position, the necessary compromise between conditions of semi-darkness and conditions of complete night lead to retaining a luminous intensity for the indicator lights of luminous push-buttons and selectors that can prove to be relatively high under conditions of complete darkness and relatively low under conditions of semi-darkness relative to guaranteeing a satisfactory visual comfort for the pilots. Moreover, in modern airplanes, the number of luminous push-buttons whose indicator lights can be illuminated simultaneously and can be found in the visual field of the pilots can be high; as a result, an increase in the discomfort of the pilots when they wish to observe what is going on outside the plane through the windshield.